This invention relates generally to remote-control manipulator apparatus, and more particularly, to an improved suspension grapple which is adapted for use in transferring nuclear fuel assemblies to a reactor core disposed in a reactor vessel or other selected locations such as, for example, a fuel storage pool. The invention also finds utility in transferring building materials to a construction site or the like.
Known suspension grapples comprise a hook mounted to a housing for selective swinging movement into or out of engagement with an article to be lifted, and a pneumatic cylinder operatively connected with the hook to effect such swinging movement. While this arrangement permits a selective actuation of the hook by simple valve operation, the need for a pneumatic cylinder and a pump, valves, piping and other components as well complicates the overall structure of the grapple, resulting in an increased production cost. The pneumatic cylinder can be operated to actuate the hook irrespective of whether it is in or out of engagement with the article. For example, if it is desired to lift an underwater fuel assembly from the fuel pool for subsequent transfer to a certain location by remote control, difficulties arise in ascertaining whether the hook is in positive engagement with the fuel assembly, being ready for lifting. If the grapple is raised with the hook not in proper lifting engagement with the fuel assembly, the assembly might fall off during transfer.
It is, therefore, an object of this invention to provide an improved remote-control manipulator apparatus which overcomes the above-stated disadvantages of the prior art apparatus.
It is another object of this invention to provide an improved suspension grapple which is adapted for use in transferring nuclear fuel assemblies to a reactor core, a fuel pool or the like and which is easy to manipulate and relatively inexpensive to manufacture as compared to conventional pneumatically operated suspension grapples.
It is a further object of this invention to provide a suspension grapple which can be operated through entirely mechanical means, thus eliminating the need for a pneumatic cylinder.
It is still further object of this invention to provide a suspension grapple which enables an operator to ascertain the presence of a proper lifting engagement of the hook with an article to be lifted.
It is still further object of this invention to provide a suspension grapple which is provided with a hook position indicator plate capable of sending a visible signal by assuming a certain position when the hook comes into proper engagement with an article to be lifted.
It is still another object of this invention to provide a suspension grapple wherein a hook position indicator plate is adapted to send a visible signal immediately after the hook comes into proper engagement with an article to be lifted.